Electrically-driven automobiles, such as a hybrid car and an EV, are becoming popular recently. An electrically-driven automobile is equipped with an inverter and the automobile runs by driving an electric motor using a power conversion function of the inverter. An in-vehicle inverter device formed of inverters in multiple systems has been developed. According to the multi-system inverter configuration, even when an inverter in anyone of the systems fails, an inverter in another system can complement to the failed inverter and vehicle driving can be continued. Consequently, reliability of vehicle driving can be enhanced.
One of problems of the in-vehicle inverter device is electromagnetic noises caused by a switching action of the inverter. Electromagnetic noises possibly trigger a malfunction of the inverter itself or a malfunction of peripheral electronic devices. Hence, there is a strong request to reduce the electromagnetic noises. As a countermeasure against electromagnetic noises, for example, PTL 1 describes an inverter device having two systems of three-phase AC inverters that drive a motor. In this inverter device, a choke coil and an electrolytic capacitor are electrically connected between a battery and a power-supply relay. The choke coil and the electrolytic capacitor together form a filter circuit so as to reduce electromagnetic noises transmitted from other devices that share the battery and electromagnetic noises transmitted from the drive device to other devices that share the battery.